(1) Field of the Invention
This invention relates to a process for producing a methacrylic resin having reduced water absorption properties.
(2) Description of the Prior Art
Methacrylic resin comprising methyl methacrylate as the main constitutional unit are not only very much excellent in transparency and weather resistance but also well-balanced in mechanical and thermal properties and fabricability, and they are widely used in various fields of application such as signboards, parts for illumination equipments, electric equipments, and automobile as well as miscellaneous goods while utilizing their advantageous features.
While on the other hand, with the development of their application uses, demands have more and more increased for the performances of the raw material resins and the improvement therefore has been desired depending on the fields of the application. One of such demands is directed to the problem of hygroscopic property. Since methacrylic resins are relatively more hygroscopic than polyolefin resins or polystyrene resins and, in view of the dimensional changes and warpage due to the moisture absorption, or generation of cracks due to the repeating cycle, of moisture adsorption and drying over a long time, their uses have been restricted depending on the commercial goods in certain application fields.
The hygroscopicity in the methacrylic resin is essentially attributable, to some extent, to the chemical structure of the polymer thereof. Then, there have been scarcely proposed means for improving the nature of them and, naturally, no attempts have been made for developing them into commercial goods up to now.
While on the other hand, it has already been recognized long since that a homopolymer of cyclohexyl methacrylate has a higher refractive index as compared with other methacrylate type polymers, as well as has an excellent light dispersing property thus having excellent basic performances as the material for plastic lenses. However, since polymer of cyclohexyl methacrylates are much brittle, it is difficult to mold under usual conditions and presents a very significant problem for putting them into practical use.